The operating principle of the label-free Epic system is based on refractive waveguide grating optical biosensors, which make very sensitive measurements of the index of refraction in a detection zone approximately 150 nm above the surface of the sensor.

The sensor configuration consists of a three-layered system: a glass substrate, a thin waveguide film within which a grating structure is embedded, and a cell/biomolecule layer. When illuminated with broadband light, the biosensor reflects a specific wavelength of light that is a sensitive function of the index of refraction close to the sensor surface. Binding events or intracellular protein movements in cells cause wavelength shifts in the reflected light that is measured with the Epic instrument (Figure 1).

The coupling of throughput and sensitivity makes the Corning Epic System an ideal tool for both biochemical and cell-based screening. Chamber temperature control variation +/- <0.25°C enables the detection of small molecules to a sensitivity of 5pg/mm2 (detecting the binding of a 300Da compound to a 70kDa target. See Figure 2). This high sensitivity enables small molecule compound libraries, macromolecules, and fragment-based screening. It also enables the use of enogenously expressing or primary cell, providing more physiologically relevant data.